ceph-facts: fix _container_exec_cmd fact value

ceph-facts: fix _container_exec_cmd fact value

When using different name between the inventory_hostname and the
ansible_hostname then the _container_exec_cmd fact will get a wrong
value based on the inventory_hostname instead of the ansible_hostname.
This happens when the ceph cluster is already running (update/upgrade).

Later the container exec commands will fail because the container name
is wrong.

We should always set the _container_exec_cmd based on the
ansible_hostname fact.

Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1795792
Signed-off-by: Dimitri Savineau <dsavinea@redhat.com>
(cherry picked from commit 1fcafffdad43476d1d99766a57b4087cfe43718b)